Reversal system for word processor

ABSTRACT

A word processing system having a typewriter as an input/output terminal and using a magnetic player/recorder for mass data storage. Controls are provided so that the printhead of the typewriter can be moved oppositely to the normal writing direction, without recording signals corresponding to such backward movement, while maintaining the proper relation between data stored in the player/recorder with the printhead position. Thus, after such backward movement when data is retrieved from the player/recorder and played out by the typewriter, it will be placed in the correct original position with respect to the text printed by the typewriter.

United States Patent [191 Heitman et al. 1 Oct. 8, 1974 I REVERSAL SYSTEM FOR WORD 3,353,648 11/1907 Amada et aI. 197/55 PROCESSOR 3,490,004 1/1970 Ross 340/ I 72.5

[75] Inventors: Richard E. Heitman, Acton; Primary Examine, Gareth D Shaw Richard C. Norris, Belmont, both of Assistant Examiner paul R. woods Mass Attorney, Agent, or Firm-Schiller & Pandiscio [73] Assignee: Arthur D. Little, lnc., Cambridge,

Mass. [57] ABSTRACT [22] Filed; Sept 22, 1972 A word processing system having a typewriter as an input/output terminal and using a magnetic player/- PP N05 291,234 recorder for mass data storage. Controls are provided so that the printhead of the typewriter can be moved [52] U.S. Cl. 340/ 172.5 oppositely to the normal writing direction without 511 1m. (:1 G11! 19/00, 01 1c 21/00 cording Signal? correspPPding Such backward [581 Field of Search 340/1725; 197/55; mOVBmem whlle maimammg the Proper relation 101/93 C tween data stored in the player/recorder with the printhead position. Thus, after such backward move- [56] References Cited meant lwheg databis {retrieved from the pllagerlrlecogder an paye out y etypewr1ter,1twi e pace in UNITED STATES PATENTS the correct original position with respect to the text 2,831,424 4/1958 MacDonald 101/93 primed b the typewriten 3,I68,l82 2/1965 Bernard et a1... 3,351,917 11/1967 Shimabukuro .1 340/1725 13 Claims, 15 Drawing Figures INPUTS FROM READ DATA CIRCUITS OR OTHER SOURCES BLANK CELL AT BUFFER INPUT CHARACTER STORE SHIFT REGISTER REGISTER OUTPUT RZA r, r

CLOCK CLOCK FIRST SUBSIDIARY STORE SECOND SUBSIDIARY PATENTED 0m 1974 saw 10 0515 OPERATOR DECO D E R ENABLE NABLE ENABLE m R1 m M2 QM T B mofiwdw 20 9 P S B P F SR D 0 BC W N%M U S T Fw YE Wm mmkmzomm 20mm RRR W M MY mm A 000 R IEEUR 122512 FFF PCPATKDPC R RRTTS PARITY CHECKER PATENTED 74 SHEU 12 (1F 15 R2 (EN 2 SHIFT REGISTER DEMULTI- PLEXER 274 46 366 S I w P 262 FORWARD L 359 I 354 370 8CD 362/ 374 COUNTER E 372 7 Q 358 555 376 /360 DATA CONVERTER BLOCK 364 378 MONO 77 28 MOTOR DISPLAY DRIVE cancuns r READ/ WRITE 233 CASSETTE HEAD F/G. ll.

REVERSAL SYSTEM FOR WORD PROCESSOR This invention relates to word processing systems and more particularly to such systems employing a typewriter as an input/output terminal coupled with an electronic memory and control system.

In the use of typewriters in connection with memories that store the typewriter operations. the backspace function may pose problems when it is desired to edit or alter the typewritten text. Typically, each operation of the typewriter by the typist is recorded in the memory. If during preparation of an initial draft a typing error occurs, it is often desirable to return the typewriter to the position at which the error occurred so that correction can be effected as by overstriking. Obviously, if the backspace key on the typewriter is used to return the typewriter elements to the desired position, each backspace will be recorded although such recording is neither needed or wanted. To obviate this problem, one prior art device provides that operation of the typewriter backspace key normally is not recorded in the memory, an additional control being provided that may be selectively used to permit deliberate recording while backspacing.

However in such prior art systems, the memory contents backspaced over may include recorded functions such as carrier index" or backspace, so that the correspondence of the typewriter print head and the recorded text becomes disordered.

In the present invention, separate means are provided for moving the printer head (or the paper carriage as the case may be) in reverse of its normal character printing motion, e.g., by stepping the typewriter printing elements left instead of in the usual direction to the right, thus permitting the backspace key to function in its normal manner. This step-left" means may be a separately operable single element or key that may be used to effect single left steps upon each depression of the key or may be a switch which changes the function of some other key on the typewriter keyboard.

It is a principal object of the present invention to provide for word-processing systems employing a linked printer and memory, improved apparatus which insures that the correspondence between the printer and the recorded text is properly maintained during step-left" operations, regardless of the nature of the recorded signals which are stepped left" over. Another object of the present invention is to provide for such a system, control means which during step-left operation examines the pertinent signal stored in the memory and moves the printing head either left, right or not at all depending upon the nature of the signal and the consequent necessary operation of the printer, or moves the contents of the memory, or moves both the memory contents and printing head, to maintain the desired printer-memory correspondence.

Other objects of the invention will in part be obvious and will in part be apparent hereinafter.

The invention accordingly comprises the appropriate possessing the construction, combination of elements, and arrangement of parts which are exemplified in the following detailed disclosure and the scope of the application which will be indicated in the claims. For a fuller understanding of the nature and objects of the present invention, reference should be had to the following detailed description taken in connection with the accompanying drawings wherein:

FIG. 1 is a perspective illustration of a typewriter and coupled console embodying the principles of the present invention;

FIG. 2 is an enlarged view of the console of FIG. l showing various control buttons, displays and other elements',

FIG. 2A is a perspective view of a standard tape cassette illustrating in phantom, the organization of information on the tape according to the principles of the present invention.

FIG. 3 is a block diagram illustrating the organization of the invention;

FIG. 4 is a block diagram showing details of the keyboard interface logic of FIG. 3;

FIG. 5 is a block diagram showing details of the buffer memory of FIG. 3;

FIG. 6 is a logic diagram partly in block form illustrating a clocking control system forming part of the buffer control of FIG. 3',

FIGS. 6A to 6D inclusive illustrate in timing diagrams on a common time base, operation of the clocking control system of FIG. 6;

FIG. 7 is a logic diagram partly in block form illustrating output multiplex, input demultiplex and read and write circuits shown in FIG. 3;

FIG. 8 is a timing diagram illustrating the operation of elements of FIG. 7;

FIG. 9 is a logic diagram partly in block form, showing the print control logic system of FIG. 3;

FIG. 10 is a diagram illustrating some logic employed in the main control of FIG. 3 for controlling clocking of the buffer memory;

FIG. 11 is a diagram, partly in block showing address display logic coupled with the control console;

FIG. 12 is a diagram illustrating logic in the main control of FIG. 3;

FIG. 13 is an additional logic diagram illustrating the main control of FIG. 3; and

FIG. 14 is yet another diagram showing additional logic cooperating with the logic of FIG. 13 to control the step left operation of the system.

Generally, the foregoing and other objects of the present invention are provided by the word processor including a printer having an output of electrical signals corresponding to operations performed on the printer, a data storage means, means for selectively coupling the output of the data storage means to the input of the printer for transcribing certain signals stored in the data storage to printed indicia and for performing other printer functions represented by other stored signals. Step-left means are included for moving the printer backwardly without recording signals corresponding to such movement. A control system is provided for moving data through the memory and for operating the printer in such manner that when the printer moves re sponsively to the step-left means, the requisite correspondence between printer position and the stored signals at the output of the memory is maintained.

This invention is generally applicable to word processing equipment incorporating a buffer memory having a feedback loop with subsidiary data storage therein, and more particularly to a word processor in which the input/output device is an electronicallycontrolled typewriter such as the type described in U.S. Pat. No. 2,919,002 (issued to L. E. Palmer) and in which the mass storage means comprises magnetic tape.

Referring now to the drawings, there is shown in FIG. I a preferred arrangement of equipment in which the invention is incorporated. The apparatus of the invention includes an input/output printer 20 interconnected by an electrically conductive cable 21 to a control console unit 22 for controlling recording, reproducing, and editing. Printer 20 typically includes a manually operable keyboard 23 for controlling a single head printer of the Palmer-type which has been adapted (for example by being emplaced on a baseplate 24 which is capable of detecting the condition of the latch and cycle shaft switches in the printer and also having solenoids capable of drifing the latches and cycle shaft of the printer) for producing an output indicative of the condition of those switches. Such a baseplate is described in US. Pat. Nos. 3,452,851 and 3,453,379 issued to L. Holmes, Jr. In printers of the Palmer type each character is automatically encoded when typed. When such a printer is combined with a Holmes type baseplate the combination will be capable of translating or interconverting formation of typed characters and performance of printing functions with corresponding coded character and function signals.

Unit 22 has a control panel 26 shown in more detail in FIG. 2, the panel including a spring-loaded, normally closed cassette door 27 which is moveable so that a magnetic tape cassette 240 (shown in more detail in FIG. 2A) can be loaded into a tape transport mechanism located behind the door. Adjacent door 27 is a display 28 for indicating a record number corresponding to the position of a data location on the tape 18 in a cassette 240 which may be loaded into the machine. n control panel 26 are also a number of keys or buttons and display lights associated with data entry, editing and playback. The system of the invention is in tended to have three basic operating modes, a draft mode, a final mode and an insert mode. To provide for selection of the mode of operation of this system there are provided a Draft button 30, a Final button 31, and an Insert button 32. To provide for control of printing out onto the printer of a character, word, or line from storage, either while the system is in draft or final mode, there are included a Character button 33, a Word button 34, and a Line button 35, plus an Automatic button 36 for allowing the system to print continuously. An On button 37 is also provided for starting the system. Stop button 38 is included for stopping any printing operation by the machine. The deleting or skipping of characters, words and lines respectively is provided by manipulation of Character, Word and Line buttons 45, 39 and 40.

A brief description of the functional consequences of the operation of the various buttons on control panel 26 will be helpful in understanding the detailed structural description of the device. It is intended that the system be capable of both recording data onto a cas sette 240 or playing data from a cassette 240 onto printer when operating in the draft mode. Specifically, it is intended during draft mode operation that any data entered by manipulation of keyboard 23 of printer 20 should be stored in a magnetic storage or record in the system with any previously recorded characters being overwritten by new data being stored at the same data locations. In order to accomplish this end one need merely start the system, select the record location, press Draft button 30 and proceed to type in data on the keyboard. To cause the data thus stored to actuate printer and therefore to be typed out, it is only necessary to return to the beginning of the stored data to push Character button 33 to obtain print out of a single character, to push Word button 34 to obtain a single word, to push Line button 35 to obtain a single line, or to push Automatic button 36 to permit the entire stored data to be reproduced on printer 20.

If one should now press Final button 31, the system is conditioned so that no storage of data manually typed or entered on printer 20 can occur, but that only the data stored in the machine can be played out on printer 20. When playing in the Final mode it will be later seen that an automatic right margin control system operates. The Draft and Final modes of operation are mutually exclusive and the system provides that if either the Draft or Final buttons are pushed, the machine is switched from the one to the other mode of operation.

Depression of Insert button 32 while the system is in the Final mode will be ineffective, i.e., will not in any sense allow the machine to operate other than in normal Final Mode operation. On the other hand, if the Insert button 32 is depressed while the system is in the Draft mode, the system switches to an Insert Mode of operation, and if desired, visual indication can be given that the machine is in an Insert Mode, as by lighting Insert button 32 or the like. The Insert Mode is intended to provide an operation such that data entered on printer 20 by manual operation of the keyboard 23 will be inserted into storage, up to a limit, without overwriting or otherwise destroying previously stored data. Only typing and recording can take place while in the Insert Mode since pushing any other buttons (except the Draft or Final buttons) on the control panel will cause the machine to trip out of the Insert mode and revert to the Draft mode. If Insert button 32 is pushed again, the system will switch out of the Insert Mode back to the Draft Mode and, of course, any visual indi cation of Insert Mode operation will terminate. If Final button 31 is pressed, the system will switch to Final mode operation.

The play or print buttons 33, 34, 35, 36 or 38 control the extent to which data will be read out of storage, either in draft or final mode operation, and displayed on printer 20. Each time Character button 33 is pushed, the next character in storage will be read out on printer 20. Similarly, depression of Word button 34 or Line button 35 will cause the next word or line in storage to be read out on the printer. When the Automatic button 36 is pushed, the system will cause the printer 26 to type out the data in storage continuously until some stopping command occurs. The latter can be obtained by pressing Stop button 38, or by certain special conditions which will be described hereinafter.

Step Right and Step Left buttons 41 and 42 control the shifting of data in storage. Each time either is pushed the data in storage is shifted by one character in the appropriate direction and the single print head 16 or carrier on the printer 20 similarly steps. In this respect buttons 41 and 42 actuate the print head 16 to move in the same manner as the space bar and backspace key on the printer keyboard 23, with certain exceptions as will be explained later. Preferably, if one of the buttons 41 and 42 is held down, repetitive action is initiated so that the system steps sequentially character by character.

As described. there are three delete/skip buttons 45, 39 and 40. When the system is in Draft mode depression of these buttons will serve to delete a recorded character. word or line from storage. When the system instead is in the Final mode, these buttons act as skip buttons which cause the system to skip the appropriate character, word or line in storage without overwriting or otherwise destroying the skipped data. Because the functioning of these buttons to cause either deletion or skipping depends upon the mode in which the system is then operating, means are provided in the form of visual indicating lights 43 and 44 which respectively light up to indicate the nature of the function of the buttons, i.e., delete or skip as the case may be.

There are two buttons for controlling tape motion, a Tape Forward button 46 and a Tape Back button 47. These are preferably of the spring-loaded type and each has a first or up position and a second or down position. Pushing either of the tape buttons 46 or 47 to its down position causes the system to move the tape 18 either back or forward (as the case may be) to the beginning of the next of a number of predetermined data blocks 19 or stations on the tape 18. This motion from predetermined station to predetermined station on the tape 18 will continue as a smooth sequence until the appropriate button is released. After release of the button, the motion of the tape 18 in the cassette 240 will continue until the next predetermined station on the tape 18 is reached, at which time the motion of the tape 18, is stopped. Similarly pushing either buttons 46 or 47 to their up position causes the system to shift to a fast forward or fast rewind movement (as the case may be) during which the tape winds continuously. Fast winding due to pushing the Tape Back button 47 to its up position will continue until the button 47 is released, at which point the system then shifts to slow forward speed and continues to move the tape until the next predetermined station on the tape is located. A similar operation in the opposite direction is effected by manipulation of the Tape Forward button.

in the preferred embodiment the cassette tape is at least a two track (25 and 29) tape, and two read/write heads, one for each of tracks 25 and 29, (or a single two-channel head such as head 238) are incorporated into the system. One of the tracks 25, of the tape is for the data to be stored. The other tape track 29 is intended to contain data addresses 48, preferably in the form of coded conversions of sequentially numbered three decimal digits, each data address 48 being physically located substantially adjacent the beginning of a data block 19 on track 25. Thus, when the tape is moved either forward or back in the cassette, circuitry associated with the address read/write head and the record number display 28 will cause the latter to be appropriately indexed each time an address corresponding to a data block or record moves past the read head. If desired, one can provide an erase mechanism associated with the tape transport mechanism and the control panel so as to erase selectively all data from the tape 18, and also if desired to regenerate the addresses on the tape 18.

Also in the preferred embodiment, associated with the control panel are a number of visual indicators or special lights 49 in addition to the delete/skip light and insert indicator light discussed earlier. These additional lights will be described later hereinafter. Similarly, a number of audio signal devices to indicate certain conditions of the apparatus can also be provided and will be described hereinafter.

The operation of the device thus described can be ad vantageously described in connection with a typewriter as an example of the printer. There are three basic situations to be described:

l. Basic entering of data through the typewriter keyboard, i.e., recording an initial draft;

2. Insertion, deletion and other operations made on data after entry of the latter, i.e., editing; and

3. Data retrieval, i.e., typing of final copy.

In order to record data initially. the operator will first activate the typewriter and also will depress button 37 to turn on the remainder of the system. The operator should first set margins and tabs on the typewriter as desired although one or more embodiments of the invention may include the ability to set and clear tabs on the basis of prior stored information. Then a magnetic tape cassette 240 is placed in the carrier behind door 27 and the operator then depresses button 30 to place the system in the draft mode of operation. The position of the tape 18 in the cassette 240 will be indicated by the address displayed at display 28. If the cassette 240 is not rewound and it is desired to start from the beginning of the cassette, the latter can be rewound by pushing Tape Back button 47 to its up position and waiting until rewind is completed. If the operator wishes to start beyond previously recorded material that is to be preserved, the tape 18 can be moved with buttons 46 and 47 until the appropriate address is noticed at display 28.

When the operator has completed the draft, a Stop Code should be entered. The Stop Code is generated by depressing the shift key and striking Stop button 38 on the control panel.

Editing of a draft can be done in three basic ways:

I. a new draft can be generated in the draft mode of operation, combining the desired parts of the old draft with typed and recorded corrections;

2. Only specific lines requiring editing can be modified; or

3. A final copy can be generated in the final mode of operation with correction being entered on the copy as the letter is typed, without recording the corrections.

Normally, the first approach would be used espe cially if further author revisions are anticipated. The third approach is appropriate if only final, minor corrections are to be made and a final copy is desired.

In generating a new draft, the following situations are likely to be encountered. First, one can edit simple typographical errors by playing back the tape 18 in the Draft mode, by first striking any one of buttons 33, 34, 35 or 36. This will cause the material recorded on the cassette to be played back on the typewriter, assuming of course that the cassette 240 has been rewound to the appropriate starting position. The material is then played up to but not through the error and the error is corrected by Overstriking. Overstriking using the keyboard 23 will automatically erase the erroneous material from the system and insert the corrected material in the appropriate place.

If the error in the draft is surplusage of material such as an extra letter or the like, it can be corrected by playing the material out on the printer 20 up to but not through the extra matter. The latter can now be deleted by simply pressing the appropriately selected one of Delete/Skip buttons 38, 39 or 40 inasmuch as these buttons generate to place the system in condition to delete the material when the system is also in the Draft mode.

If the error in the Draft mode is due to missing material, the latter can be added by playing out the recorded material (in the draft mode) up to the appropriate position, pushing lnsert Button 32 and typing on keyboard 23 the missing characters or words. The machine can then be taken out of the Insert mode simply by pushing any of the buttons 33 to 36 inclusive, all of which when actuated switch the system back to the Draft mode of operation.

Final copy can be typed in either the Draft or Final mode. in typing out copy, the basic difference in operation between the two modes is simply that in the draft mode the system will execute each carrier return signal that has been recorded whereas, in the final mode the carrier returns may or may not be executed depending upon the operation of an automatic right margin control feature.

if no further editing is required, the operator merely inserts paper into the printer 20, sets the tabs and margins of the latter, puts the cassette 240 into the machine, and moves it to the beginning of the record with buttons 46 and 47. The machine then is placed in automatic play by striking Automatic button 36. The material or text stored in the machine will now be played out on the printer on a substantially continuous basis until the printing is stopped by either striking Stop button 38 or because the operator has preferably recorded an appropriate Stop Code at the end of each page of text. If manual entry of certain material such as the name and address of the person to whom a letter is to be sent is to be inserted on the final copy, a Stop Code should have been recorded when the original draft was recorded so that automatic printing stops at the point where the special material is to be manually entered. In order to prevent a recording of the manually entered material if the system is not operating in the final mode, the system should then be switched temporarily to that mode of operation by depressing button 31.

If the final copy is being printed out in the Final mode of operation, the system will stop printing whenever it detects that it cannot automatically find a carrier return opportunity such as a recorded Carrier Return or Space or Hyphen signal in a predetermined return zone adjacent the right margin of the printed text. When this occurs, the operator may use key 33 to cause automatic printing, character by character, up to the point where a Hyphen and a Carrier Return can be manually entered on the keyboard 23 after which automatic typing can then be reinitiated, e.g., by again depressing the Automatic key 36. Normally, this manually entered Hyphen and Carrier Return will not be recorded so that any returns from the same tape will encounter the same stopping conditions. If, however, the operator wishes to record the Hyphen and Carrier Return, this may be done by pressing Draft button and lnsert button 32, typing the Hyphen and Carrier Return, then pushing Final button 31 to switch the system operation back to Final mode, and finally pushing one of the buttons 33-36 inclusive to resume printing. As long as no further changes are made in the paragraph up to this point, subsequent reruns will always find the Carrier Return and hyphen when needed and will continue playing without automatically stopping.

ln typing copy, it may be necessary to make some minor corrections in the recorded material. As long as these changes need not be recorded on the tape, the procedure is simple while operating in the final mode. Simply by depressing any of the Delete/Skip buttons, 39,40 and 45, one may cause the system to skip over unwanted characters, words, or lines in the material being played back and additional material may be manually typed in.

Before describing some of the more complex editing operations, it will be advantageous to describe briefly the general organization of the system embodying printer 20, baseplate 24 and control console unit 22. With reference particularly to FIG. 3, there is shown a block diagram of the organization of a system in simplified form. In order to clarify the diagram, all of the con trol connections are shown as solid lines whereas all of the data carrying lines are shown as dashed lines, The embodiment of FIG. 3 includes input/output printer 20 which, as previously described, is connected via base plate 24 to the control console. Data flow from the printer 20, in the form of electrical signals, is applied to keyboard interface logic 50. The latter primarily serves to encode electrical signals from the printer 20. The output of the interface logic 50 is then fed along an appropriate connection to the input of a buffer memory 52. As will be described later, the buffer memory S2 is preferably in the form of a shift register capable of storing, for example, 200 characters each of eight bits.

It will be appreciated that one may however employ a random access type memory such as a core array as memory 52, but because a random access memory might involve complex addressing logic, a shift register type of memory is preferred. The output of the buffer memory 52 in turn is connected to means such as a multiplexer 54 for converting the eight parallel bit per character format of the data organization in the buffer memory 52 to a serial train of data bits. The output of multiplexer 54 is then in turn fed to the input of write data circuitry 56 which conditions the data and places it in single-channel format for storage, such as on the tape 18 in a cassette 240 mounted in a magnetic recording apparatus indicated as data storage 58.

Alternatively, if one employs an eight-track tape with corresponding read-write channels, data need not be multiplexed but can be read out directly from buffer storage to tape.

The organization shown in FIG. 3 also includes a return path for reading data out of data storage 58 so that it can be printed out by printer 20. To this end, data storage 58 is connected to read-data circuits 60 and to read-address circuits 63. The latter is intended to read the address track 29 on the two-channel tape 18 and provides an output which is connected to address display logic 64 which serves to actuate address-display 28. Readdata circuits 60 are intended to read the data stored in serial form on the other track 25 of the tape 18. The output of read-data circuits 60 is fed to means, such as input demultiplexer 62, for converting the serial form of the data into an eight parallel bit per character code, suitable for injection into the buffer memory. To that end the output of demultiplexer 62 is coupled to the input of buffer memory 52. The output of buffer memory 52 is also connected as an input to both margin-adjust logic 66 and print-control logic 68. Margin-adjust logic 66 serves to examine the contents of 

1. A system for processing data in conjunction with the formation of characters and the performance of selected functions by printing apparatus having printing means for forming printed characters on a record medium, a carrier for said record medium, means for converting each character and function performed by said apparatus into a corresponding signal, data storage means for storing a plurality of said coded character and function signals, means for moving said carrier and printing means relative to one another in increments of distance in alternative opposite first and second directions along a line, said system comprising in combination; means for passing said signals through said storage means so that said signals become available sequentially at the output of said storage means in either a sequence corresponding at least in part to relative motion of said carrier and printing means in said first direction or reversal of said sequence; means for examining the output of said storage means to determine the nature of the signal thereat; control means for controlling the relative movement of said printing means and carrier, and being coupled to said means for examining so as to be responsive to the nature of the coded character and function signals becoming available at said output; said control means comprising means for effecting relative movement of said carrier and printing means in said second direction when and only when the nature of the signal at the output of said storage means is such as to represent a character or function requiring relative motion of said carrier and printing means by one of said increments in said first direction, without recording in said data storage means any signals corresponding to said movement in said second direction, and means for effecting passage of said signals through said storage means so as to maintain the original order of correspondence between each signal examined at said output and the relative position of said carrier and printing means.
 2. A system as defined in claim 1 wherein said storage means has a storage capacity of n characters and wherein said means for moving said signals through said storage means can, by moving said signals in cycles of n-1 characters each time, effect a reversal in said sequence in which said signals become available at said output.
 3. A system as defined in claim 1 wherein said control means comprises means for effecting relative movement in said first direction by one of said increments when the nature of said signal at the output of said storage means is such as to represent a function requiring relative motion of said caRrier and printing means by one increment in said second direction.
 4. A system as defined in claim 1 wherein said control means comprises means for effecting passage of said signals through said storage means by one step in said sequence when the nature of said signal at the output of said storage means is such as to represent only empty storage capacity in said storage means.
 5. A system as defined in claim 1 wherein said control means comprises means, responsive to the availability at said output of each signal having a nature representative of a function which does not require said relative motion of said carrier and said printing means in either of said directions, for effecting a single-step reversal of said sequence in which said signals become available at the output of said storage means.
 6. A system as defined in claim 1 wherein said control means comprises means, responsive to the availability at the output of said storage means of a signal having a nature representative of a function which requires uninterrupted relative motion of said carrier and printing means in said first direction over a plurality of said increments; a. for effecting reversal of said sequence in which said signals become available at the output of said storage means until the nature of the signal at said output is representative only of empty storage capacity in said storage means, and b. for effecting relative motion of said carrier and printing means in said second direction to the beginning of said line.
 7. A system as defined in claim 1 wherein said data storage means comprises a shift register.
 8. A system for processing data in conjunction with the formation of characters and the performance of selected functions by printing apparatus having a printing head, movable along a line in increments of distance for forming printed characters on a record medium, and control means for controlling said apparatus to form said characters sequentially and responsively to coded character signals along said line in a first direction and to perform said functions responsively to corresponding coded function signals, said system comprising in combination: data storage means for storing a plurality of said coded characters and function signals; means for moving said signals through said storage means so that said signals become available at the output of said storage means either in a sequence or a reversal of said sequence; means for examining each signal available at the output of said storage means; and means for coupling said means for examining to said control means so that said control means is responsive to coded character and function signals at the output of said storage means, said control means comprising means for effecting movement of said printing head in a second direction opposite to said first direction when the examined signal represents a character or is a function requiring motion of said printing head by one of said increments in said first direction and means for effecting any reversal in said sequence in which said signals become available at the output of said storage means necessary to maintain the original order of correspondence between the position of said printing head and the signals available at said output.
 9. A system as defined in claim 8 wherein said printing apparatus is a typewriter having a carrier for said record medium, said carrier being movable in a direction substantially normal to said line, and wherein said functions include the typewriter functions of tab, tab set, tab clear, carrier index, space, backspace and carrier return.
 10. A system as defined in claim 9 wherein said control means comprises means for effecting movement of said printing head in said first direction by one of said increments where the signal available at the output of said storage means corresponds to said backspace function.
 11. A system as defined in claim 9 wherein said control means comprises means for effecting movement of said signals through said storage means by one step in said sequence when said signal available at the output of said storage means is only representative of empty storage capacity in said storage means.
 12. A system as defined in claim 9 wherein said control means comprises means, responsive to the availability at the output of said storage means of any signal corresponding to said tab set, tab clear and carrier index functions, for effecting a reversal by a single step of said sequence in which said signals become available at the output of said storage means.
 13. A system as defined in claim 9 wherein said control means comprises means responsive to the availability at the output of said storage means of a signal corresponding to said tab function, for effecting a reversal of said sequence in which said signals become available at said output until the signal appearing at said output is representative only of empty storage capacity in said storage means, and for effecting motion of said printing head in said second direction to the beginning of said line. 